It is perfectly possible to write off PAS leader Hadi as an elderly bigot unable to see the modern world, and the modern Malaysia, as they really are. If he was alone in his outdated bigotry no one would need to pay him any attention.
The danger that he represents is that he will be able to convince members of the Malay Malaysian community that they, and their religious beliefs, are endangered by the existence and activities of Chinese Malaysians.
To preach that line is actively dangerous to peace and stability in the country. Whether he is too bigoted to realise this, or just does not care, is somewhat beside the point. If allowed to pursue his blatant communal activity he may endanger peace in the country and will, at the very least, engender hate and resentment where comradeship should be.
The responsible authorities should consider an in depth enquiry to determine whether he is breaching the law by his rabble rousing and, if so, prosecute him